When is a lipoma not a lipoma? Case report presenting a lipoblastoma-like tumor of the gluteal cleft in an older gentleman with literature review

Lipoblastoma-Like Tumor of the Tongue With IDH1 Mutation: A Case Report and Literature Review

BACKGROUND

Lipoblastoma-like tumors (LLTs) are uncommon lipogenic neoplasms that predominantly occur in the vulva of female individuals. This study presents a novel case of LLT located on the tongue with an IDH1 mutation. Both the site of occurrence and molecular alterations are reported for the first time.

CASE PRESENTATION

A 65-year-old female patient presented to the hospital 1 month ago with an incidental finding of a multinodular mass at the right lingual margin. We performed an incision along the outer edge of the mass and completely excised it 0.5 cm beyond its periphery. The final pathological diagnosis after routine examination confirmed a lipoblastoma-like tumor. Furthermore, Next-generation sequencing revealed the presence of mutations in IDH1.

CONCLUSIONS

This study presents the first documented case of LLT, thereby expanding its anatomical site of tongue and confirming the presence of a significant IDH1 mutation, thus enhancing our understanding of the molecular alterations in LLT.

Giant Angiomyofibroblastoma With a Florid Lipomatous Component: A Report and Review of Diagnostic Considerations

Angiomyofibroblastoma is a benign, usually small neoplasm typically constituted by spindle-shaped and epithelioid cells in a vascularized, myxoid-fibrous stromal background. It is most often seen in the superficial genitalia of female patients of reproductive age. However, various clinical and histologic features have been reported, including tumors in male patients, malignant transformation, extragenital sites, huge sizes, and a prominent lipomatous pattern. We report the clinical and pathologic features of one such tumor: a 23.5 cm lipomatous angiomyofibroblastoma of the vulva in a 40-year-old female patient. We also discuss important diagnostic considerations when approaching such large tumors, particularly in the setting of a biopsy specimen.

Lipoblastoma-like tumor of the inguinal region: a close mimicker of myxoid liposarcoma

Lipoblastoma-like tumor is a rare mesenchymal neoplasm, typically arising in the vulvar region of young women. Although it is considered a benign tumor, rare local recurrences and exceptionally distant metastases have been reported. Histological examination reveals a well-circumscribed tumor with lobulated pattern, composed of a mixture of mature adipocytes, spindle cells and lipoblasts set in abundant myxoid stroma with numerous thin-walled capillary-like vessels. Due to the rarity of this neoplasm and its morphological resemblance with other benign and malignant lipomatous tumors, the diagnosis of lipoblastoma-like tumor is often challenging. Herein, we present a case occurring in the inguinal region of a 28-year-old woman. Histological examination showed a mixture of mature adipocytes, bland-looking spindle cells with fibrillary cytoplasm, and numerous univacuolated lipoblasts set in a prominent myxoid matrix containing numerous thin-walled branching vessels. Immunohistochemically, neoplastic cells showed diffuse immunostaining for CD34 and negativity for α-smooth muscle actin, desmin, Rb1, MDM2 and STAT6. The main differential diagnoses included myxoid liposarcoma, spindle cell lipoma and cellular angiofibroma. FISH was negative for DDIT3; moreover, no evidence of regional gain or loss of RB1 was identified by FISH. Based on morphological, immunohistochemical and cytogenetic/molecular findings, a final diagnosis of "lipoblastoma-like tumor" of the inguinal region was rendered.

Expanding the Clinicopathologic and Molecular Spectrum of Lipoblastoma-Like Tumor in a Series of 28 Cases

Lipoblastoma-like tumor (LLT) is a rare adipocytic neoplasm with a predilection for the vulva. Since 2002, <30 cases have been reported, characterizing it as an indolent tumor that may sometimes recur locally. Diagnosis can be challenging due to its rarity and morphologic overlap with other adipocytic tumors. Thus far, there are no specific molecular or immunohistochemical features to aid in the diagnosis of LLT. Recent case reports have described LLT arising at other sites, including the spermatic cord and gluteal region, suggesting wider anatomical distribution. We present a large series of LLT to further characterize its clinicopathologic and molecular features. Twenty-eight cases of LLT were retrieved from departmental and consult archives (including 8 from a prior series). The cohort comprised 28 patients (8 males, 20 females) with a median age of 28 years (range: 1-80 years). There were 17 primary LLT of the vulva. Other anatomical sites included the scrotum (n = 3), spermatic cord (n = 2), inguinal region (n = 2), limbs (n = 2), pelvis (n = 1), and retroperitoneum (n = 1). Median tumor size was 6.0 cm (range: 1.8-30.0 cm). The tumors had a lobulated architecture and were typically composed of adipocytes, lipoblasts, and spindle cells in a myxoid stroma with prominent thin-walled vessels. Using immunohistochemistry, a subset showed loss of Rb expression (12/23 of samples). Follow-up in 15 patients (median: 56 months) revealed 8 patients with local recurrence and 1 patient with metastases to the lung/pleura and breasts. Targeted DNA sequencing revealed a simple genomic profile with limited copy number alterations and low mutational burden. No alterations in RB1 were identified. The metastatic LLT showed concurrent pathogenic PIK3CA and MTOR activating mutations, both in the primary and in the lung/pleural metastasis; the latter also harbored TERT promoter mutation. One tumor had a pathogenic TSC1 mutation, and one tumor showed 2-copy deletion of CDKN2A, CDKN2B, and MTAP. No biologically significant variants were identified in 8 tumors. No gene fusions were identified by RNA sequencing in 4 tumors successfully sequenced. This study expands the clinicopathologic spectrum of LLT, highlighting its wider anatomical distribution and potential for occasional metastasis. Molecularly, we identified activating mutations in the PI3K-MTOR signaling pathway in 2 tumors, which may contribute to exceptional aggressive behavior.

Recurrent 8q11-13 Aberrations Leading to PLAG1 Rearrangements, Including Novel Chimeras HNRNPA2B1::PLAG1 and SDCBP::PLAG1, in Lipomatous Tumors

BACKGROUND/AIM

Structural abnormalities of chromosome bands 8q11-13, resulting in rearrangement of the pleomorphic adenoma gene 1 (PLAG1), are known to characterize lipoblastoma, a benign fat cell tumor, found mainly in children. Here, we describe 8q11-13 rearrangements and their molecular consequences on PLAG1 in 7 lipomatous tumors in adults.

MATERIALS AND METHODS

The patients were 5 males and 2 females between 23 and 62 years old. The tumors, namely five lipomas, one fibrolipoma and one spindle cell lipoma, were examined using G-banding with karyotyping, fluorescence in situ hybridization (FISH; three tumors), RNA sequencing, reverse transcription (RT) PCR, and Sanger sequencing analyses (two tumors).

RESULTS

All 7 tumors had karyotypic aberrations which included rearrangements of chromosome bands 8q11-13 (the criterion for selection into this study). FISH analyses with a PLAG1 break apart probe showed abnormal hybridization signals in both interphase nuclei and on metaphase spreads indicating PLAG1 rearrangement. RNA sequencing detected fusion between exon 1 of heterogeneous nuclear ribonucleoprotein A2/B1 (HNRNPA2B1) and exon 2 or 3 of PLAG1 in a lipoma and fusion between exon 2 of syndecan binding protein (SDCBP) and exon 2 or 3 of PLAG1 in a spindle cell lipoma. The HNRNPA2B1::PLAG1 and SDCBP::PLAG1 fusion transcripts were confirmed using RT-PCR/Sanger sequencing analyses.

CONCLUSION

As 8q11-13 aberrations/PLAG1-rearrangements/PLAG1-chimeras may evidently be a defining pathogenetic feature of lipogenic neoplasms of several histological types and not just lipoblastomas, we suggest that the term "8q11-13/PLAG1-rearranged lipomatous tumors" be generally adopted for this tumor subset.